1. Field of the Invention
The present invention relates to tire sensors for remotely monitoring tire pressure, methods of manufacturing same, and methods of using same. More particularly, the invention relates to a Hall effect tire sensor in mechanical, electromechanical and electronic versions.
Due to recent sport utility vehicle rollover deaths and accidents in the United States, there has been a great deal of attention focused on under-inflated tires and low tire pressure. As the center of gravity for SUV's is higher than for other vehicles, proper tire pressure is more critical. We need to prevent rollover accidents. As is common in the American culture, due to negligence tire pressure is allowed to get to low levels without maintaining the proper inflation for optimum safety in operating the vehicle. Low tire pressure can create many problems, including poor vehicle performance, increased wear of the tires, and elevated tire temperatures which will ultimately ruin the tire.
For tires being utilized on the popular sport utility vehicles where the center of gravity is particularly high when the vehicle is loaded with passengers and cargo, an under-inflated tire poses a special risk for rollovers. As one will recall, Ford Motor Company's car, the Ford Explorer, utilizing Bridgestone Tires, experienced an extraordinary number of rollovers and highway deaths as a result. According to statistics, in an attempt to correct that situation, the Ford Motor operator's manual, according to news stories, suggested that tires be over inflated in order to provide a safer ride. However, consumers, when confronted with the tire pressure monitor at a gas station-type coin operated air compressor, would fill the tire to the limits which are labeled on the side of the tire rim. It was proposed by plaintiffs' attorneys that a normal operator could not be expected to know the contents of the owner manual when the tire pressure was clearly labeled on the side of the tire.
Needless to say, in the above-mentioned criteria, a critical factor for safe operation of a vehicle is maintaining a proper air pressure within the tires. In reality, car operators ignore tire pressure until it becomes clearly apparent that the tire pressure is so low that the tire looks like it is going flat. On many occasions, this low tire pressure situation is allowed to continue, perhaps for months at a time.
Over the course of time, the tires remain in this potentially dangerous situation until the inflation has been restored to a proper level. Therefore, in accordance with their findings, the United States Congress passed the Transportation Recall Enhancement, Accountability, and Documentation Act (TREAD) in October of 2002. In the TREAD Act, there is a requirement that all new motor vehicles shall have a warning system to indicate to the operator when a tire is significantly under inflated. In order to provide a tire pressure monitoring system that complies with the TREAD Act, many companies have launched research projects to provide such a tire pressure system, that is highly reliable, does not experience confused signals, and one which will always indicate to the car operator when a dangerous situation exists. Generally, there is a warning light on the dashboard on the car to be connected, whether through wires or wireless transfer, to the tire pressure monitor system in the communication with the individual tires on the vehicle.
2. Description of the Prior Art
In the recent past, conventional RF transmitter tire pressure monitors and SAW device sensors have become well known in the art, including one of the most common types of tire sensors, a tire sensor that includes an RF transmitter for sending the signal.
However, practitioners of those inventions have become aware of certain problems which are presented by those prior art inventions. One particular problem that has plagued users has been that the RF transmitters become confused when two (2) cars get too close to one another. There are other complexities which give rise to a lack of reliability.
Various prior art configurations have been proposed to provide a tire pressure monitoring system which complies with the TREAD Act requirements. However, there have been problems inherent with each of those prior art methods and apparatuses, in that most of them included a radio communication device with a central radio receiver in the vehicle, which was powered by a battery. The present inventor has found that battery powered devices are prone to failure when the battery wears out, rendering the device unreliable, or at worst providing a lack of reliability on an intermittent basis which would be undetected by the operator. In addition, many of the devices which utilize a SAW device and/or piezoelectric pulsing, and the older type of reed switches, are speed sensitive and prone to unreliability because as the tire gets moving, pressures change, and problems are caused.
Although all of the prior art devices are technically feasible in principle, they also have several serious drawbacks. One of them is the sheer complexity of the device, which makes it susceptible to reliability issues. As the whole purpose of a tire pressure monitoring system is to increase safety, the system itself has to have a very high standard of reliability. And, as automotive engineers are aware, reliability is normally and inversely proportional to the complexity of the system.
Besides the complexity of the prior art systems, there are other issues relating to the reliability, which include the fact that most prior art systems need to be installed within the tire itself, in order to give a solid pressure reading. It would be a great advantage for a system that could be mounted on the valve stem, as the system could be interchanged with tires, as they were rotated around a vehicle, or changed, etc. This desired feature would dramatically increase the reliability of the tire pressure monitoring system, as is needed under the TREAD Act.
Yet one more problem experienced by the prior art that utilizes a radio signal, is the problem of confused signals when one car, and its radio frequency generating system, gets too close to another vehicle with a similar system. For instance, your car, as you are speeding down the highway, comes within several feet of another car in the lane next to you, and your receiver may pick up the signal which is given off by your neighbor's vehicle. A warning light would appear on your dashboard, and you would pull over to the nearest gas station in order to fill tires, which may be perfectly fine. Conversely, the vehicle which has a low tire pressure may pick up a signal from your vehicle, which indicates that their tires are perfectly fine, when in fact they may not be. One can imagine the confusion when there are hundreds of millions of transmitters and receivers (four transmitters and one receiver per every vehicle) which would all be on the highways, and potentially very close to one another. There would be millions of potential interference and misidentification situations arising. Again, due to the high level of complexity of this system, the cost is greatly inflated over simpler, more reliable systems.
And finally, the high cost and complexity of the presently available tire monitoring systems is so great that automobile manufacturers resist utilizing them, and are actively looking for alternatives that provided both a high level of reliability combined with cost effectiveness. Therefore, it would be most advantageous to provide a tire pressure monitoring system which simple, reliable, and inexpensive.
Further, it would also be a great advantage to make the system easier to install on a valve stem, rather than in the interior of the tire, whereby it will be easier to replace worn out tires and easier to rotate tires with a simpler system.
It would be of a great advantage to the automotive industry if there was provided a tire sensor monitoring system that does not rely on batteries or radio antennas, and method of making the same, and a method of using the tire sensor.